Iterate Transformation should support passing contant parameters

Use Case: Call a subproject with a mix of parameters from a table (iterate) and constant parameters (like in Call another project transfomation)

e.g. Iterate over a list of files and call a sub project for each file, but use a constant file parameter, that is used in the subproject to load additional data.

This would also apply to Iterate table transformation.

Good point. We will add this in v3.8.

Available starting from version 3.8.